Add support for refreshing feed icons

[rystaf]

Refetch feed icon if the icon url included in the feed changes or if feed is refreshed manually.

Resolves #1555 #1805

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• I have tested my changes
• I read this document: https://miniflux.app/faq.html#pull-request

[rystaf]

I removed the RefreshIcon option I added to the feeds. This was to enable an automatic check for icon changes. Now instead of just checking everytime, I'm keeping track of the icon_url in the feed table and triggering a download if it's changed.
I'm also trying out removing the feed_icons table entirely and storing the icon_id directly in the feeds table

[mattxtaz]

I removed the RefreshIcon option I added to the feeds. This was to enable an automatic check for icon changes. Now instead of just checking everytime, I'm keeping track of the icon_url in the feed table and triggering a download if it's changed.

What about if the site changes the favicon image but does not change the URL? Or can you just delete the URL completely and let Miniflux automatically detect it again? I want a way to make it refresh the icon even if the URL hasn’t changed

[rystaf]

@mattxtaz with this PR, clicking the "Refresh" link on the feed page would remove the feed icon and trigger miniflux to redownload it.

[fguillot]

How do you backfill the icon_url field? If I understand correctly, this field is updated only when a new icon is created or when someone force refresh the feed manually.

[rystaf]

How do you backfill the icon_url field? If I understand correctly, this field is updated only when a new icon is created or when someone force refresh the feed manually.

The icon_url will match what ever is included in the feed. It gets updated when the feed is updated.

[fguillot]

How do you backfill the icon_url field? If I understand correctly, this field is updated only when a new icon is created or when someone force refresh the feed manually.

The icon_url will match what ever is included in the feed. It gets updated when the feed is updated.

What about feeds that don't specify an icon URL explicitly in their feed?

The logs will have this message below but that can leads to confusion because the icon_url is always empty in the DB:

level=DEBUG msg="Feed icon not modified" user_id=1 feed_id=1 feed_icon_url=""

Tested with few feeds:

miniflux2=# select feed_url, icon_url from feeds;
                   feed_url                   |               icon_url
----------------------------------------------+---------------------------------------
 https://www.lemonde.fr/rss/une.xml           |
 https://linuxfr.org/news.atom                |
 https://blog.alexellis.io/rss/               | https://blog.alexellis.io/favicon.png
 https://miniflux.app/feed.xml                |
 https://github.com/miniflux/v2/releases.atom |
(5 rows)

[rystaf]

icon urls that were discovered by fetching the feed's website are not included here since checking for changes would require refetching the feed's website on each update.

I updated the log message to read "feed icon url not modified" and only if an icon_url is set.